1. Field of the Invention
The invention relates to a liquid-crystal display with a liquid-crystal layer which can be switched between two optically different states (rest state, excited state), and two support plates which enclose the liquid-crystal layer between them and carry on their surfaces facing each other respective electrically conducting coatings (electrodes) as well as an orientation layer, where at least one of the two orientation layers consists of a polymer.
2. Description of the Prior Art
Such a display, in which the polymer layer is rubbed and aligns parallel to the plates, is described in German Published Non-Prosecuted Application No. 25 48 925.
In almost all types of display, the liquid molecules must have a certain orientation in the non-switched state. This rest state texture is generated nowadays as a rule by suitably prepared orientation layers on the carrier plates. A number of techniques have been developed in the meantime by which practically any desired molecule orientation can be brought about and can be held over long periods of operation. In view of this high state of development it is particularly unsatisfactory that it has not been possible to date to suppress the following side effect: An orientation layer which preorients the liquid crystal properly has, in general, so high an orientation force that it prevents adjacent liquid crystal molecules from being transferred into the new state or order when the switching voltage is applied. Fringe disturbances remain which degrade the optical qualities (less picture contrast, limited viewing angle range) and limit the number of possible multiplex steps, since the voltage-contrast characteristic is flattened in its transition range. One could, of course, attempt to decrease the texture faults by higher switching voltages. Voltage increases, however, increase the drive requirements and are furthermore possible, with dynamic addressing, only within very narrow limits, since in multiplex operation, the effective on-voltage is interlinked with the effective off-voltage, and both voltages must always bracket the transition region of the voltage-contrast characteristic.